The research described in this proposal has two objectives: l) to determine the age at which children use nonverbal and linguistic indicators of possession or ownership to govern their sharing and defense of desirable objects, and 2) to assess the specific affect of two particular indicators of possession (words denoting possession such as "yours" and the physical possession of an object by another child) on preschoolers' sharing, defense of objects, and attempts to take another's possession, i.e., to determine if these indicators of possession elicit behavior consistent with adult conceptions of how individuals should treat their own and others' possessions. In the first study, 40 preschoolers (aged 2 1/2 to 5 years) will be told that an attractive toy is either theirs to keep or belongs to the class. Each subject will then be observed for 10 minutes in a controlled setting and will be interviewed to assess their understanding of possessive words. The data will be analyzed to determine at what age children adjust their sharing behavior and defense of objects to comply with norms relating to ownership, and if the comprehension of concepts of possessions develop coincident with such changes in behavior. The second study will assess the extent to which preschool children of different ages vary their behavior in accordance with nonverbal indicators of possession. Half of the children will be observed (in groups of 3) in a situation involving an attractive toy which belongs to no one (it will be sitting in th room when all three children arrive). The other children will also be observed for ten minutes in groups of 3; however, for these groups one child will enter the room first and, thus, will have possession of the toy when the two other children arrive. The data will be analyzed to determine at what age children equate possession of an object with ownership. It will also be possible to assess differences in the behavior of a "rightful" owner (a child with a prior claim to a toy) and a child who dominates a toy but did not possess the toy before anyone else.